As a conventional reliability estimation method for detected information, there is a method of preparing a digital watermark signal orthogonal to a two-dimensionally embedded digital watermark signal (a first pattern array) as a second pattern array, calculating, with a detected value detected using this second pattern array as a reference, a distance between the detected value and a detected value detected by using the first pattern as a “reliability distance”, and statistically verifying the reliability distance to thereby judge reliability of detected information (see, for example, Patent Document 1).
Patent Document 1: JP 2001-119558 A